Corrosion-driven droplet wetting on iron nanolayers

Area of Science:

• Materials Science
• Electrochemistry
• Surface Science

Background:

• The classical Evans' drop experiment involves an aqueous salt solution on a metal surface, leading to pit formation and oxide deposits due to metal dissolution.
• Understanding corrosion-induced droplet dynamics is crucial for predicting material degradation and designing protective coatings.

Purpose of the Study:

• To investigate corrosion-induced droplet spreading on iron nanolayers using optical methods.
• To elucidate the relationship between corrosion propagation, electrolyte droplet behavior, and substrate properties at the nanoscale.

Main Methods:

• Utilized semi-transparent iron nanolayers to enable simultaneous optical monitoring of iron corrosion and electrolyte droplet dynamics.
• Observed pit growth, merging into a corrosion front, and its interaction with the droplet's triple contact line.

Main Results:

• Corrosion pits grew and merged under the droplet, forming a distinct corrosion front that reached the triple contact line.
• The corrosion front initiated non-radial spreading of the droplet, eventually propagating beyond the immobile electrolyte.
• Chemically-active wetting was observed only on conductive substrates with strong iron nanofilm adhesion; weaker spreading was noted on thick iron films.

Conclusions:

• Corrosion-driven electrochemical reactions can induce significant wetting phenomena at the nanometer scale, altering droplet behavior.
• The findings suggest new perspectives on substrate wetting influenced by corrosion processes, particularly in systems with conductive substrates and nanofilms.
• Further research is needed to fully explore the implications of these nanoscale electrochemical wetting behaviors.